Postage meters are mass produced devices for imprinting a defined unit value for governmental or private carrier delivery of parcels and envelopes. The term "postage meter" also includes other like devices which provide unit value printing such as tax stamp meters. Postage meters include internal accounting devices which account for postage value representation which is stored within the meter and is printed by the meter. The postage printed by the meter is adjustable or settable through a value selection system to any value, within a range of values, selected by the postage meter user. The accounting for postage printed by the meter is stored only within the meter. As a result, postage meters must possess an extremely high reliability to avoid the loss of user or governmental funds stored within the meter.
Postage meters are often used in systems wherein the mail piece which is to receive a postage stamp impression, is transported to the postage meter for imprinting. Systems of this type have been proposed which are coupled to scales to weigh the mail piece to determine the appropriate postage. The scale mechanism in such systems may be connected to the postage meter to cause the postage meter value selection mechanism to operate to set the postage meter print elements to the appropriate postage for the weight of the mail piece weighed and to be transported to the postage meter.
It has been recognized that electronic postage meters are particularly suited for systems applications, such as the system described above. This is, in part, because electronic postage meters are adapted to be electronically interfaced with scale mechanisms so that the value selection mechanism of the postage meter can be controlled by a signal generated by the weighing device and coupled to an input port of the electronic postage meter.
Examples of electronic postage meters are disclosed in U.S. Pat. No. 3,938,095 for COMPUTER RESPONSIVE POSTAGE METER; U.S. Pat. No. 3,978,457 for MICROCOMPUTERIZED ELECTRONIC POSTAGE METER SYSTEM; and, in U.S. Pat. No. 4,301,507 for ELECTRONIC POSTAGE METER HAVING PLURAL COMPUTING SYSTEMS. In postage meters of the type disclosed in the noted U.S. patents, the accounting mechanism and the value selection mechanism are electronically controlled. The memory function in the electronic accounting circuits have replaced the function served in mechanical postage meters by mechanical accounting registers. The motor or solenoid operated, electronically controlled, setting mechanism have replaced the function served in mechanical postage meters by levers and thumbwheels. Both the accounting circuits and value selection system in such postage meters may be operated under microcomputer control.
The value selection system must operate accurately in adjusting the postage meter printing mechanism to an appropriate selected postage value to be imprinted. An error in the value selection mechanism could result in a loss of funds to either the user or government. Additionally, such an error could result in a mail piece being imprinted with a deficiency in the postage stamp value such that the governmental or private carrier will refuse or delay delivery of the parcels and envelopes, and/or, require additional postage to be paid over the amount printed on the mail piece, by either the sender or recipient.
In systems applications, it is desireable to increase the number of mail pieces which are imprinted with a postage stamp within a given unit of time without sacrificing the accuracy and reliability of the meter including the meter setting mechanism. By increasing the throughput, the productivity of the postage meter system is enhanced, diminishing the unit handling cost to the postage meter user of each mail piece. Nevertheless, because postage meters print unit value and are accounted for by no other mechanism than the postage meter accounting registers, the value set in the print mechanism must accurately reflect the value intended.
In recognition of the criticality of the postage value selection function, postage value selection confirmation systems have been incorporated in the electronic postage meter systems disclosed in U.S. Pat. No. 3,938,095 and U.S. Pat. No. 3,978,457.